1. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis1 Dr. L. Morgenroth CASE GmbH

2. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis2 PACS Thermal Model PACS TMM: 7 Boundary Nodes 185 Diffusion Nodes Input-Status: 22. Feb. 2002 Model includes: - all Mechanisms - all Harness - Possibility of transient Analysis - Radiation Environment Model excludes: - Cryostat TMM

3. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis3 PACS Heat Dissipation (with 20 % margin)

4. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis4 PACS Boundary-Temperatures (stationary) These temperatures are stationary ESTEC-results from Feb. 2002. The transient behavior of the boundary temperatures is neglected. The optical bench temperatures are about 2 to 2.5 K higher than the values used for the analysis in September 2001. -> Higher Flux from Optical Bench through Struts to Level 1

5. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis5 PACS Detector-Temperatures (depending on Copper-Type for Cooling-Straps)

6. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis6 Sensitivity of PACS Temperatures (to varying Boundary-Temperatures)

7. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis7 Sensitivity of PACS Heat Fluxes Uncertainty in CFRP properties: If the predicted conductivity of the CFRP of the PACS suspension struts would be doubled, the average heat load to Level 1 increases from 11 to 16 mW. Measurements are intended.

8. PACS IBDR 27/28 Feb 2002 PACS Thermal Analysis8 Summary The average PACS heat dissipation is 2.9 mW (2.9 - 3.3 mW) to LHe and 11.0 mW (9.0 - 12.4 mW) to Level 1. The main difference to the results of the analysis from Sept. 2001 is an increase of the average dissipation to Level 1 by about 2.4 mW. This mainly results from higher optical bench temperatures. The sensitivity of the PACS-Detector temperatures to the boundary temperatures is low. It is recommended to use high-conductivity-Cu for the cooling-straps of the Red Spectrometer and the Photometer and standard-ISO-Cu for the Blue Spectrometer. For transient calculations with transient Level 1- and Optical Bench- temperatures a TMM of the Cryostat has to be included.